Method and apparatus for harvesting and implanting bone plugs

ABSTRACT

A system for transplanting a bone plug from a donor site to a recipient site extracts the bone plug from the donor site, and then places a bone plug delivery device having a tip which is at least translucent and, preferably, clear over a tube containing the bone plug. The tip is then placed substantially over a pre-formed hole in the recipient site, whereafter the bone plug is forced from the tube, through the transparent tip, and into the pre-formed hole.

This application is a divisional application of U.S. patent applicationSer. No. 09/118,680, filed on Jul. 17, 1998 U.S. Pat. No. 6,359,011which is incorporated in its entirety by reference.

BACKGROUND OF THE INVENTION

The present invention is directed to methods and apparatus forharvesting and implanting bone plugs. The invention has particularutility in repairing damaged bone tissue, such as articular cartilageand underlying subchondral cancellous bone in the knee and otherweight-bearing joints.

Weight-bearing joints, such as the knee, are particularly susceptible toinjuries caused by friction between opposing bone surfaces. Tounderstand the causes of such injuries, it is first necessary tounderstand the anatomy of a such a joint. In this regard, FIG. 1illustrates knee joint 10. As shown in FIG. 1, knee joint 10 connectsfemur 12 to tibia 14 and fibula 18 via connective tissue 15 and 17Interposed between opposing surfaces of femur 12 and tibia 14 arelateral and medial meniscus cartilages 21 and 23, respectively. Condyles22 at distal end 11 of femur 12 are supported by meniscus cartilages 21and 23 on proximal end 13 of tibia 14. Normally, distal end 11 of femur12, including condyles 22, is covered by layer 28 of cartilaginousmaterial which is about 5 mm thick. This layer 28 is called thearticular cartilage.

Articular cartilage 28 forms a generally resilient pad which is fixed todistal surface 11 of femur 12 in order to protect femur 12 from wear andmechanical shock. When lubricated by fluid in knee joint 10, articularcartilage 28 provides a surface which is readily slidable on theunderlying surfaces of meniscus cartilages 21 and 23 or on proximalsurface 13 of tibia 14 if one or both of meniscus cartilages 21 and 23is partially or totally absent. Problems arise, however, if articularcartilage 28 becomes injured due to excessive near. For example,articular cartilage 28 can become torn or thin, or holes can developtherein. As a result of such injuries, osteochondritis and/or arthritiscan develop, making movement of the joint painful In extreme cases,these conditions can result in disability if not treated.

Injuries of the foregoing type can be treated by replacing the joint, orportions thereof, with artificial materials. In some cases, however, itis possible to treat the injury by replacing only the bone tissue (i.e.,the articular cartilage and/or underlying bone) at the site of theinjury with a graft, or plug, from a healthy site. This option ispreferable for a number of reasons. For example, surgery to transplant abone plug is less invasive than that required for a joint replacement.In fact, bone plug transplant surgery is typically performedarthroscopically. Moreover, transplanting bone plugs leads to fewerpost-operative complications, a shorter rehabilitation period, andbetter results overall, since it actually leaves patients with theiroriginal joint intact.

Surgical techniques for transplanting bone plugs typically involveremoving the damaged bone tissue by drilling or cutting a hole at thesite of the damage, and plugging this hole with a bone plug extractedfrom healthy bone tissue in the patient's body. This healthy tissue isgenerally extracted from non-load-bearing joints or surfaces in order tominimize patient substantial discomfort.

Surgical instruments are currently available which may be used toharvest or extract a bone plug from a donor site and, then, to implantit into a pre-formed hole at a recipient site. A conventional harvestinginstrument typically includes a tube having a cutting edge at the distalend. To extract a plug, the instrument is driven into the bone at thedonor site and then removed, taking with it a plug of healthy bonetissue.

The conventional instruments for harvesting bone plugs described abovesuffer from several drawbacks. For example, it is difficult to regulatethe size (i.e., the length) of bone plugs extracted by them. Moreover,the bone plug tissue is sometimes unduly damaged or traumatized byexcessive forces exerted during extraction or implantation.

Conventional instruments for implanting bone plugs also suffer fromdrawbacks. Generally, it is difficult to gauge the exact depth of pluginsertion and, thus, to avoid slight protrusions or cavities. Thisproblem is compounded in those instances where the donor and recipientsites do not have matching surface contours.

Thus, there exists a need for a bone plug harvesting apparatus which canbe more easily used to remove plugs of bone, and which enables a surgeonto regulate the size of the bone plug being removed. In addition, thereexists a need for a bone plug implantation apparatus which permits theplug to be implanted level and in proper alignment with the surroundingbone.

In view of the foregoing, an object of the invention is to provideimproved methods and apparatus for harvesting and implanting bone plugs.

Another object is to provide such methods and apparatus as to permit thesize of extracted plugs to be better regulated.

Still another object of the invention is to provide such methods andapparatus as to minimize trauma to the transplanted plugs.

Still another object is to provide such methods and apparatus as tofacilitate accurate placement of bone plugs during implantation.

Yet still another object is to provide such methods and apparatus as tofacilitate implantation in instances where the plugs or recipient siteshave uneven contours.

SUMMARY OF THE INVENTION

The present invention addresses the foregoing needs by providing, in oneaspect, a bone plug implantation apparatus having a translucent and,preferably, a transparent or clear tip, through which the bone plug canbe viewed during implantation. Unlike the prior art, inclusion of such atip permits the surgeon to view the bone plug during implantation,thereby facilitating better placement, alignment and insertion of theplug into the donor site.

According to further aspects of the invention, the apparatus includes a“harvesting” tube which can be used to harvest the plug and which isused to hold the bone plug prior to implanting. The apparatus can alsoinclude a push rod that forces the bone plug into a pre-formed hole atthe transplant site. The harvesting tube can include an aperture orrecessed inner wall that reduces friction on the plug duringimplantation (and harvesting) and that, thereby, reduces undesirablecompression of the plug.

According to further aspects of the invention, the tip has an innerdiameter substantially equal to that of the hole into which the boneplug is transplanted. An outer diameter of the tip, however, can begreater than that of the hole. This larger outer diameter forms ashoulder upon which the tip can rest during implantation. The tip alsocovers the distal end of the harvesting tube and, hence, minimizes thedamage that it might otherwise cause at the transplant site.

In still further aspects of the invention, the tip is rotatable relativeto the harvesting tube. This facilitates rotation of the bone plugrelative to the transplant site, e.g. so that their respective surfacescan be aligned and otherwise better fitted

According to still another aspect, the present invention provides anapparatus for harvesting plugs from bone tissue. The apparatus includesa harvesting tube, as described above, to which a cutting sheath isfitted. The sheath, which includes a cutting edge and a cutting tooth,can include markings on its outer surface so that the depth ofinsertion—and, therefore, the length of the bone plug—can be determinedduring harvesting. The harvesting tube can likewise include markings onits outer surface, e.g., adjacent the aforementioned window, so that theposition and length of the plus can be more accurately determined afterharvesting.

According to still another aspect, the present invention provides amethod of transplanting a bone plug from a donor site to a recipientsize. The method includes harvesting the bone plug from the donor siteutilizing a bone plug harvesting apparatus as described above. Theharvesting tube of the harvesting apparatus is fitted with a tip asdescribed above to form a bone plug implantation apparatus, also asdescribed above. The tip of the implantation apparatus is placed over apre-formed hole at the recipient site and the bone plug is forced fromthe tube, through the transparent tip, and into the pre-formed hole. Inrelated aspects of the invention, the tip is rotated prior toimplantation to assure a better fit.

Still further aspects of the invention provide a drill guide for use inbone plug removal and replacement. The guide comprises a tip and aharvesting tube as described above. A drill bit is guided through theassembled tube/tip and is used to form a hole at the recipient site. Useof such an assembly as a drill guide can improve the integrity of thetransplant, e.g., if the same (or similar) tube and tip are subsequentlyused during implantation of the plug.

This brief summary has been provided so that the nature of the inventionmay be understood quickly. A more complete understanding of theinvention can be obtained by reference to the following detaileddescription of the preferred embodiments thereof in connection with theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention may be attained byreference to the drawings, in which:

FIG. 1 shows the anatomy of a knee joint;

FIG. 2 shows a representative embodiment of a harvesting tube used in abone plug harvesting apparatus in accordance with the present invention;

FIG. 2A shows a top view of the apparatus shown in FIG. 2;

FIG. 2B shows a bone plug harvesting apparatus according to theinvention.

FIGS. 3 and 4 show cutting teeth used in the apparatus of FIG. 2B;

FIGS. 5 through 10 depict a method for harvesting a bone plug using theapparatus shown in FIG. 2B;

FIGS. 11 through 13 show components of a bone plug implantationapparatus of the present invention;

FIG. 14 shows a bone plug implantation apparatus of the presentinvention:

FIG. 15 shows damaged bone tissue comprised of articular cartilage andunderlying bone;

FIGS. 16 through 21 depict a method of implanting a bone plug using theapparatus shown in FIG. 14.

FIGS. 22-23 show drill guides according to the invention for formingbone holes.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIGS. 2 and 2B are front views of a device 30 according to the inventionfor harvesting a plug of bone tissue (i.e., bone and/or articularcartilage) from a donor site. Illustrated device 30 is generallyconfigured in the manner of the harvesting apparatus described inco-pending, commonly assigned U.S. patent application Ser. No.08/866,830, filed May 30, 1997, the teachings of which are incorporatedherein by reference. The harvesting device 30 incorporates improvementson the apparatus of that prior application, as described below andelsewhere herein.

The device 30 includes harvesting tube 31, connector 32, handle 33, andcutting sheath 35. As shown in FIG. 2, handle 33 is attached to proximalend 34 of tube 31 and is used to facilitate driving the distal end ofthe device into the donor site and rotating the device to remove theplug. Illustrated handle 33 can be rod-like in construction, asillustrated, or it can be of other configurations, such as a knurledknob, hexagonal nut, or the like.

A connector 32 disposed at the junction of handle 33 and tube 31includes axial threads 36, as illustrated, to facilitate affixing acutting sheath or, alternatively, a delivery tip to the harvesting tube.Of course, connector 32 is not limited to the configuration shown inFIG. 2 but, rather, can be of other configurations sufficient to supportthe uses described below

Tube 31 is substantially cylindrical in shape and is made of surgicalstainless steel or other material suitable to be driven into bone andused for plug extraction, as described below Tube 31 has an inner bow 39(see FIG. 2B) extending at least part way (and, preferably, all the way)along longitudinal axis A—A thereof (including through handle 33 andconnector 32 as shown in FIG. 2A). The bore 39 has a diameter sized inaccord with the bone plugs to be harvested. A tapered edge 41 at thedistal end of the tube 31 which facilitates movement of a bone plug(i.e., articular cartilage and/or underlying bone) into and out of innerbore 39.

Referring to FIG. 2B, device 30 also includes cutting sheath 35 that,too, is fabricated from surgical stainless steel or other suitablematerial. The sheath includes, at its distal end, tooth 43 and cuttingedge 48. An inner bore receives tube 31 in the manner shown in FIG. 2B.The proximal end (e.g. the hub) 38 of sheath 35 includes threading orother structures for mating with corresponding threading 36 on connector32.

The outer surface of cutting sheath 35 may also include one or moremarkings 35 b, as shown in FIG. 2B, to facilitate determination of adepth to which tube 31 and cutting sheath 35 are inserted into bonetissue and, thereby, to facilitate estimating the length of a harvestedbone plug. In preferred embodiments of the invention, there are aplurality of such markings on cutting sheath 35, each of which isseparated by a predetermined distance which, in preferred embodiments ofthe invention is roughly 5 mm.

Tooth 43, coupled (e.g., welded, clued or integrally formed)substantially at or near distal end 40 of sheath 35, extends into innerbore 39 in a direction substantially orthogonal to cutting edge 48 asshown. By rotating the tube 31, tooth 43 undercuts the bone within thebore 39 and, thereby, facilitates removal of the bone plug. Although aplurality of such teeth may be used in the present invention, preferredembodiments thereof include only one such tooth.

FIGS. 3 and 4 show front views of tube 31, cutting sheath 35, inner bore39 and tooth 43 taken along ling B—B of FIG. 2B Referring to FIG. 3,tooth 43 is preferably rectangular in shape, though it may be of otherconfigurations, e.g., triangular (as shown in FIG. 4) The tooth 43 has alength which is roughly 1 16 to ¼ the diameter of inner bore 39, withthe most preferred length being roughly ⅕ of the diameter of inner bore39.

Turning back to FIGS. 2 and 2B, tube 31 includes at least one recess 45cut at least partway from an inner surface of tube 31 to an outersurface. This may comprise an indentation or, preferably, a window oraperture cut entirely through tube 31. To avoid unduly weakening thetube 31, recess 45 is spaced apart from its distal end.

Recess 45 is positioned so that at least a portion of it penetrates apatient's bone tissue during bone plug extraction. In this regard, therecess 45 reduces frictional contact between the bone plug and the innersurface of the tube 31. This has the advantage of reducing undesirablecompression of the plug during extraction and subsequent emplacement.Though the illustrated embodiment incorporates only a single recess 45,those skilled in the art will appreciate that multiple recesses (e.g.,windows) of varying (or the same) configuration may be used.

As further shown in the drawing, the outer surface of tube 31 may alsoinclude one or more markings, as shown in close-up view 46 in FIG. 2. Inthe illustrated embodiment, these markings are substantially similar tothose contained on cutting sheath 35 and described above. When used inconjunction with a window-like recess 45, these markings facilitatedetermination of the length and position of the bone plug.

FIGS. 5 to 10 depict the distal end of device 30 during a surgicalprocedure for harvesting a bone plug in accordance with the presentinvention. By way of overview, they show the driving of tube 31 andcutting sheath 35 into donor site 50, the rotation of the tube toundercut the bone plug with tooth 43 and the removal of the tube 31 withthe bone plug The surgical techniques shown in these drawings aretypically performed arthroscopically using conventional equipment,although open surgical techniques may be used as well

In detail, FIG. 5 shows a close-up view of the distal end of device 30(i.e., the distal end of cutting sheath 35 and the distal end of tube31) prior to contact with donor site 50. In this case, donor site 50comprises bone tissue made up of both articular cartilage and underlyingbone, such as the intracondylar notch or the periphery of the condyle.It should be noted, however, that the invention can also be used withcartilage-only and with bone-only sites, as well as with otherappropriate bodily structures.

FIGS. 6 and 7 show penetration of device 30—in particular, the distalend of tube 31 and cutting sheath 35—into donor site 50. Cutting edge 48slices through donor site 50 to separate the bone plug 52 fromsurrounding tissue 54. Tapered edge 41 of tube 31 facilitates movementof bone tissue into inner bore 39 of tube 31.

Once tube 31 has been driven into donor site 50 a desired depth, e.g.,as determined from markings 35 b, the bone plug 52 is further separatedfrom the surrounding tissue by rotating device 30 (and, moreparticularly, cutting sheath 35) to undercut the plus 52, as shown inFIG. 8. Once rotated a complete (or near-complete) revolution, thedistal end of device 30 is pulled from donor site, taking bone plug 52with it. This is shown in FIGS. 9 and 10.

After extraction of the plug 52, cutting sheath 35 is removed (e.g.,unscrewed and removably slid from) tube 31, leaving bone plug 52 in tube31. Bone plug 52 may then be implanted from tube 31 into a recipientsite using the implantation apparatus shown in FIG. 14, the separatecomponents of which are shown in FIGS. 11 to 13

At the outset, the implantation apparatus includes a harvesting tube 31similar and, preferably identical to that shown in FIG. 2 and describedabove. For sake of completeness, that tube is redrawn in FIG. 11.

The implantation apparatus further includes a delivery tip 67 thatfacilitates transfer of the bone plug into a pre-formed hole in therecipient site. The tip 67, which is attachably affixed to the distalend of the tube 31 is “at least translucent,” i.e., it is translucentor, preferably, transparent and, still more preferably, clear. In thisregard, the tip 67 is preferably fabricated from surgical gradeplastics, or the like.

Tip 67 can be affixed to tube 31, via threading, friction fit or otherknown mechanism, so that its inner bore 101 is substantially alignedwith inner bore 39 at the distal end of tube 31. In the preferredembodiment, the tip is part of a one-piece, molded device which alsoincludes a sheath-like portion—referred to below as proximal segment66—that slips over tube 31 and screws onto connector 32 (e.g., in thesame manner as the cutting sheath discussed above) via connector 71.Like tip 67, the proximal segment 66 of the illustrated embodiment isalso fabricated from materials that are at least translucent (and,preferably, clear). Together, the tip 67 and proximal segment 66 arereferred to as delivery sheath 65.

Of course, the invention is not limited to using a one-piece, moldeddevice as its delivery sheath. For example, the delivery sheath can be atwo-piece device comprised of a tip and a tube which fasten together,e.g., via screw threads or the like.

Referring to FIG. 12, proximal segment 66 has an inner bore 100 with adiameter substantially similar to, but somewhat larger than, an outerdiameter 70 of tube 31. This permits segment 66 to fit over tube 31without substantial lateral play. Preferably, the connector 32 and/orconnector 71 are mated to one another so as to permit rotation of thesheath 65 (and, more particularly, the tip 67) relative to the tube 31.In the illustrated embodiment, the mating threads of corrector 32 andconnector 71 permit it such rotation (e.g., via clockwise orcounterclockwise motion of one relative to the other) Alternativeembodiment may incorporate bearings, floating or sliding surfacesinstead.

Tip 67 preferably has an inner bore 101 with a diameter thatsubstantially corresponds to that of inner bore 39 of the distal end ofharvesting tube 31. In preferred embodiments, this also correspondssubstantially to the inner diameter of the plug-receiving cavity at therecipient site.

The outer diameter of at least the distal end of the tip 67, however, ispreferably larger than the inner diameter of the cavity. The surface ofthe tip 67 at the distal end is preferably smooth, so as to preventmarring of the bone tissue surface, though it may include afriction-enhancing coating or structure (e.g., protrusions) to helpmaintain alignment of the bores 39 and 101 with the recipient cavityduring the procedure.

The tip 67 and, more particularly, inner bore 101 has a length thatpermits at least a portion of the bone plug 52 to be seen during theimplantation procedure. Thus, in preferred embodiments, the bore 101 hasa length of 1 to 50 mm and, preferably, about 10 mm. Of course, thediameter of bore 101, like that of the distal end of tube 31 and therecipient cavity, substantially matches the expected diameter of thebone plug 52.

The junction of bores 100 and 101 forms a chamfered or flat shoulderadjacent to, or upon which, the distal end of tube 31 is disposed. Thisprevents the tube 31 and, particularly, its tapered distal end, fromdirectly contacting, and potentially marring, the surface of therecipient site. In this regard, preferably, the distal end of tube 31does not actually contact the shoulder. Instead, edge 41 is held justproximal of the shoulder (i.e., by connector 71 and threads 34) so as topermit transfer of a bone plug into the tip

Referring to FIG. 13, the illustrated implantation apparatus includespush rod 74 that slides, reciprocates or otherwise moves within innerbore 39 of tube 31 to push bone plug 52 through the tip 67 and into therecipient bore hole. To this end, the rod 74 is long enough andotherwise sized to permit complete evacuation of the plus from the bores39 and 101. The distal end of rod 74 is preferably sized and shaped(e.g., flat) to effect little or no damage to bone plug 52 during itscontact therewith. To prevent the push rod from moving into tube 31, therod 74 preferably has a head 77 greater in diameter than inner bore 39.

The following describes implantation of a bone plug into a recipientsite using the implantation device shown in FIGS. 11 to 14. As before,this surgical technique is preferably performed arthroscopically usingconventional equipment, although open techniques may be utilized aswell. Implantation is generally performed in the manner described in theaforementioned incorporated-by-reference application, as modified toaccommodate the improvements described herein.

To begin, FIG. 15 shows a defect or damaged area 79 in articularcartilage 80 of the type amenable to repair using the method andapparatus of the present invention. Prior to implantation, the defect ordamaged area is removed and a hole for the bone plug is formed.

This may be accomplished in a variety of ways known in the art.Preferably, however, the bone hole itself is formed using the harvestingtube 31 and/or delivery sheath 65 as a drill guide. More specifically,the tube 31 and sheath 65 (with substantially clear tip 67) areassembled and placed over the recipient site. A drill bit, having anouter diameter which is substantially the same as bore 39, is thenpassed through bores 39 and 101 and applied to form a hole in the bone.FIG. 23 shows drill bit 150 of drill 151 forming a bone hole in thismanner. Alternatively, the tip of delivery sheath 65 alone may be usedto form the bone hole FIG. 22 shows drill bit 152 of drill 153 forming abone hole in this manner In this regard, forming a bone hole using drillguides having a substantially clear tip facilitates formation of boneholes normal to the bone surface or at other desired angles. It alsoensures better aliment between the bone plug implanting device and thehole at the recipient site. That is, because the drill bit can be viewedthrough the clear tip, it is possible to align the drill bit moreaccurately than has heretofore been possible. This step is, of course,performed prior to harvesting the replacement bone plug 52 or,alternatively, is performed using a harvesting tube 31 other than thatin which a harvested plug 52 is contained.

Once the bone hole has been formed and the replacement bone plug hasbeen harvested, the implantation apparatus is assembled by sliding thedelivery sheath 65 over the harvesting tube 31. The assembled apparatusis then placed so that the bore 101 substantially aligns with bone hole87, and so that edge 88 of tip 67 (i.e., that portion which surroundsthe inner bore) rests on the surrounding bone tissue surface (i.e., onthe articular cartilage covering the underlying bone).

If desired, the rod 74 may be used to move the bone plug 52 at leastpartially into tip 67 prior to placement of the implantation apparatus.Indeed, the bone plug 52 may be partially extruded, e.g., 1 mm to 2 mm,from the tip 67 to facilitate its alignment and insertion into the bonehole 87. The bone plug 52, moreover, can be rotated for better alignmentwith the hole. This may be accomplished by rotating the implantationdevice as a whole or, preferably, by rotating just the implantationsheath 65.

FIG. 17 shows the beginning of the implantation process, with push rod74 forcing bone plug 52 from the inner bore 39, into tip 67 and justinto bone hole 87. As additional downward pressure is applied to pushrod 74 bone plug 52 is forced further into the bone hole Once again, theplug 52 may be oriented before it is fully implanted. e.g., to obtain abetter alignment to the bone surface contour, by rotating theimplantation sheath 65 relative to the harvesting tube 31.

In this latter regard, since tip 67 is clear, the surgeon is able toview at least part of, and preferably the entirety of, the plug 52during implantation. In the example shown in FIG. 18, the surgeon willsee that top surface 91 of bone plug 52 does not align with surface 94of the recipient site. Accordingly, as shown in FIG. 19, the sheath 65is rotated in the direction of arrow 95 for proper orientation. Oncealignment has been achieved, the push rod 74 can be tapped to finalizethe implant, as shown in FIG. 20. Thereafter, tube 31 and device 65(including push rod 74) are removed from the site, as shown in FIG. 21.

In a preferred embodiment, bone plug 52 and corresponding bone hole 87are sized for an interference fit, so as to reduce the chances that thebone plug will inadvertently dislodge from the bone hole. In thisregard, although the bone plug preferably has an interference fit in thebone hole, several alternative methods are available for maintaining thebone plug in the bone hole. One such technique involves sewing suturesthrough peripheral edges of the articular cartilage adhering to the boneplug and the surrounding articular cartilage tissue. Alternatively, anadhesive layer (not shown) may be provided between bone plug 52 and bonehole 87. This adhesive layer allows time for sufficient ingrowth oftissue from the surrounding environment so that bone plug 52 may becomelocked into place in bone hole 87. Various bio-adhesives are well knownin the art, examples of which are fibrinogen and thrombin sealant (see,e.g., U.S. Pat. No. 5,067,964).

Bone-growth and cartilage-growth promoting chemical factors may also beadded to the bone hole and/or to the implanted bone plug in order topromote rapid reconnection of the bone plug to the surrounding bone andarticular cartilage. These bone-growth and cartilage-growth promotingchemical factors may include cartilage-derived colony-stimulating factor(“CDGF”) (see U.S. Pat. No. 5,376,636), various interleukins,colony-stimulating factor (“CSF”), osteopontin, platelet-derived growthfactor (“PDGF”), and bone morphogenic protein (“BMP-1”). See also U.S.Pat. No. 5,373,503, the contents of which are hereby incorporated byreference into the subject application as if set forth herein in full.

The present invention has been described with respect to particularillustrative embodiments. It is to be understood that the invention isnot limited to the above-described embodiments and modificationsthereto, and that various changes and modifications may be made by thoseof ordinary skill in the art without departing from the spirit and scopeof the appended claims.

In view of the foregoing, what we claim is:
 1. A method of transplantinga bone plug from a donor site to a recipient site, the method comprisingthe steps of: harvesting the bone plug from the donor site; attaching atip at least a portion of which is at least translucent over a tubecontaining the bone plug; placing the tip substantially over apre-formed hole in the recipient site; forcing the bone plug from thetube, through the tip, and into the pre-formed hole.
 2. A methodaccording to claim 1, further comprising the step of rotating the tiprelative to the tube.
 3. A method according to claim 1, wherein the tubecomprises an inner bore, a cutting edge coupled to the tube, and a toothcoupled to the cutting edge, the tooth extending towards the inner borein a direction substantially orthogonal to the cutting edge; and whereinthe harvesting step comprises the steps of: driving the tube into thedonor site, cutting-edge-first; rotating at least the cutting edge sothat the tooth cuts through the bone so as to separate at least part ofa bottom surface of the bone plug from the donor site; and removing thetube containing the bone plug from the donor site.
 4. A method accordingto claim 3, further comprising the step of determining an amount thatthe driving step has driven the tube into the first area of the bone byreading one or more markings disposed relative to the cutting edge.
 5. Amethod according to claim 1, wherein the bone plug comprises articularcartilage and underlying bone tissue.
 6. A method according to claim 1,further comprising, before the harvesting step, the step of forming thepre-formed hole using at least the tip.
 7. A method according to claim6, wherein the forming step forms the pre-formed hole by placing thetube from within the bone plug delivery device over the recipient site,passing a drill bit through the tube, and drilling through bone tissueat the recipient site via the tube.
 8. A method according to claim 7,further comprising the step of adjusting an angle of the drill bit basedon a view of the drill bit as the drill bit passes through the tip.